Magnetically rotating constricted arc-discharge device

ABSTRACT

A combination comprising a constricted arc-discharge device having electromagnetic means associated therewith to rotatably direct a resultant magnetic flux generally transverse to and intersecting the constricted arc-discharge maintained during operation. The magnetic flux interacts with the constricted arcdischarge causing it to rotate about the longitudinal axis of the arc-tube. The luminous efficiency of the combination is very high, and the rotation of the discharge prevents early failure of the device.

United States Patent Inventors Appl No Filed Patented Assigncc MAGNETICALLY ROTATING CONSTRICTED ARC-DISCHARGE DEVICE 10 Claims, 12 Drawing Figs.

US. Cl v.

315/343; 3l3/l5 Int. Cl H01] 17/14 Field of Search Robert J. Zollweg Monroeville, and Walter J. Burnham, Pittsburgh, Pa.

Westinghouse Electric Corporation Pittsburgh, Pa. a corporation oi Pennsylvania I60, l6l 3l5/34l 342, 343, 344, 346

ARC-TUBE POW SUPPLY I 5 6 1 References Cited UNITED STATES PATENTS 2,042,140 5/1936 Bunger 315/343 Primary l;'xaminerRaymond F. Hossfeld AtturneysA. T. Stratton, W. D. Palmer and Walter Sutcliff PowE'R SUPPLY FOR MAGNET PATENTEOFEB 9|97l I 3552583 sum 1 OF 3 I [g H 20 i t 30o [34 22) 24c 24c 26 ARC-TUBE PowE'R AR'c-TuBE Esra SUPPLY POWER STJ P E$ FOR MAGNETS] SUPPLY FOR ETS 2'2 30b 20.4 #1 |s-L l6 FIG. I. l4 FIG. 3.

WITNESSES: INVENTORS Y Robert J. Zollweg' and g6, Walter J. Burnhom.

BY m @VW 9 6%,

ATTORNEY PATENTEUFEB slsm 3,562,583

sum 3 0F 3 Q FlG.9A.

l M Q 40 POWER SUPPLY H FOR MAGNETS 56 440 \44c POWER/ 44b SUPPLY FOR MAGNETS MOTOR F IG; 8.

FIG. 9B.

MAGNETICALLY ROTATING CONSTRICTEI) ARC- DISCHARGE DEVICE CROSS-REFERENCE TO RELATED APPLICATION This application is related to the concurrently filed, commonly assigned application of Westinghouse Electric Corporation Case Number 40,210, Ser. No. 794,202, filed Jan. 27, 1969, entitled Convective.Arc-StabilizationbyRotation."

BACKGROUND OF THE INVENTION is established between the input of energy via the arc, and the radiation and the conductive heat losses'to and through the walls. This stable temperature distributionis in effect a resultant of design considerations which include the selection of discharge-sustaining materials, electrode general arc-tube design parameters.

With the addition of metal halides to such devices the arcdischarge during high power level operation tends to become constricted to the central axis of the arc-tube when the partial pressure of the discharge-sustaining constituents reach relatively high pressures. This constricted arc-discharge does not remain along the central axis of the arc-tube during continued operation but bows outward or drifts about within'thearcspacing and tube. The self-magnetic field'of the constricted arc-discharge may be responsible in part for such deviation from the longitudinal axis of the arc-tube. This are bowing can and generally does result in early lamp failure throughexcessive heating of a particular portion of the arc-tube wall. Other problems which it raises are possible reactions of the arc-tube wall with high temperature species of the discharge-sustaining materials.

It is well known that in highpressure mercury vapor lamps operated at high power input levelsin a horizontal burning position, such lamps tend to have a hot upper portion of the arc-tube, presumably from convection effects on the discharge materials. Electromagnetic means have been used to deflect the arc-discharge back to a more central position within the arc-tube by directing the magnetic field transverse to the arc current direction wherein the interaction of the mutually perpendicular arc-discharge current and the magnetic field results in a force which is likewise mutually perpendicular according to electromagnetic principles. I

A relatively stable temperature distribution is desirable in arc-discharge devices since thecool spottemperature of the interior arc-tube will determine the partial pressures of the various constituents. In a bowed, constricted arc lamp condensation of constituents may occur at the portion of the arctube which is furthest away from the bowed arc-discharge. By constricted arc-discharge is here meant-one wherein a visible hot core carries most of the arc current. This central core occupies only a relatively small portion of the total arc-tube volume.

SUMMARY'OF THE INVENTION a constricted arc-discharge device comprising the arc-tube and discharge-sustaining filling, such that upon operation of said device at the design power input a constricted arcdischarge is established between the electrodes of the device, and electromagnetic means are provided for rotatably directing a resultant magnetic field generally transverse to the constricted arc-discharge. The resultant magnetic field intersects the arc-discharge, interacting with it so that the resulting motor action produces a force which causes the bowed arcdischarge to rotate about the longitudinal central axis of the arc-tube.

The electromagnetic means can be incorporated as part of the arc-discharge device itself, or can be part of a fixture used in combination with the arc-discharge device.

The resultant magnetic field is predetermined to provide a force, upon interaction with the arc-discharge current, which is a design parameter, such that the constricted arc-discharge rotates about the central longitudinal axis of the arc-tube, at a distance from the arc tube axis. The magnetic field should not be so strong that it drives the are up against the interior wall of the arc tube. It is preferred that the arc-discharge be forced into rotation along a path about midway from the arc-tube longitudinal axis and the arc-tube wall.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an embodiment of the inventive combination,

FIG. 2 is an end view of a portion of FIG. 1;

FIG. 3 is a schematic view of another embodiment of the invention;

FIG. 4 is an end view of a portion of FIG. 3;

FIG. 5 is a front elevational view of a combination lighting fixture and arc-discharge device as an embodiment of the invention;

FIG. 6a and 6b describe the voltage waveforms and mag-- netic flux vectors resulting from the operation of the embodiment shown in FIG. 1;

FIG. 7a and 7b describe the voltage waveforms and mag netic fiux vectors resulting from the operation of the embodiment shown in FIG. 3;

FIG. 8 is a schematic of another embodiment of the inventive combination; and

FIG. 9a and 9b are a schematic of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the preferred embodiment shown in FIG. I, the arc-tube 10 comprises a hermetically sealed generally tubular envelope 12, which is composed of a high-temperature-resistant, lighttransmitting material such as quartz. The electrical lead-in conductors 14 are sealed through the press sealed end por-' tions 16 of the tubular envelope via conventional molybdenum ribbon seals 18. The lead-ins 14 support operably disposed electrodes 20 within the arc-tube. The electrodes are aligned along the longitudinal axis of the arc-tube. The electrodes 20 comprise tungsten wire coiled over atungsten base member, with or without electron emissive material coated thereon. A discharge sustaining filling is provided within the arc-tube, which is for example an 18 mm. id, 70 mm. are

path, about 20 cc volume arc-tube designed for 400 watt power input. As an example, the filling comprises 50 mg. of mercury, 20 mg. of cerium iodide, 20 mg. of dyspro'sium iodide, and an easily ionizable starting gas, suchas argon at 20 torrs. Other discharge-sustaining fillings'can be utilized in practicing the present invention. The fillings disclosed by US. Pat. No. 3,334,261, issued Aug. 1, 1967, with or without additional metallic additives, particularly -give rise to the constricted arc-discharge condition when operated at high power levels and discharge migration which is controlled and corrected utilizing the present invention. The electrical lead-ins 14 are cxtemally electrically connected to the discharge power supply 22 which can be a conventionally'ballasted AC or DC power supply.

The electromagnetic means in FIG. I comprise the conductive coils or turns 24a, 24b, 240, which are spaced from and symmetrically disposed about the arc-tube, and the power supply 26 to which the turns are electrically connected.

When a DC power supply is utilized as the arctube power source 22, the power supply 26 is simply a three phase source of suitable voltage and frequency. The conductive turns are designed to provide a predetermined resultant flux density value at the symmetrical center of the arc-tube, along the arctube longitudinal axis. This resultant flux density is to be determined with respect to the arc-discharge current so that the motor action force produced by their interaction causes the arc-discharge to rotate at a distance spaced from both the arc tube central longitudinal axis and the arc-tube wall. The force is preferably determined so that the rotating arcdischarge is approximately midway between the arc-tube longitudinal axis and the arc-tube wall. For example, when the arc-tube described in the foregoing is connected as the load for a 200 VDC ballasted supply, and the lamp carries about a two amp current, the resultant flux density produced at the central portion of the arc-discharge path along the longitudinal axis is about 5 X e bers per square meter. This flux density can be readily supplied by a few turns of 014 wire carrying several amps current, the turns aligned in planes about 0.5 cm. from the arc-tube wall. The turns can be made rectangular to conform to the generally used arc-tube supports, and can also perform this support function.

The operation of this embodiment of the present invention can be best described by reference to accompanying FIG. 1 and FIG. 6a and 61;. Power supply 26 provides a conventional three phase AC voltage waveform as illustrated in FIG. 6a. The coils 24a, 24b, 246 are wired in the same sense, i.e., a particular polarity waveform applied to each coil will produce the same current direction in each of the coils, in this case a positive polarity waveform will cause a clockwise flow of current in each coil. This means that when current is flowing clockwise the magnetic flux produced by that particular coil will be directed toward the arc-tube, and when the voltage waveform polarity reverses the magnetic flux direction is in the opposite direction. The instantaneous voltage waveform applied to each coil is analyzed in FIG. 6a and 6b, with the vector of the magnetic flux produced by the particular coil and the resultant magnetic flux also being represented. The analysis proceeds from 2,, and it is readily seen how the resultant directivity of the magnetic flux is rotatably directed. Thus, during operation of this combination there is produced a rotatably directed resultant magnetic flux which is substantially perpendicular to the arc-discharge. The relatively constant amplitude, rotatably directed resultant magnetic flux interacts with the constricted are giving rise to a continuous force upon the arc-discharge, which force is rotational as a result of the rotational directivity of the magnetic flux. The force is instantaneously mutually perpendicular to both the arc current and the magnetic flux, according to electromagnetic principles, thus causing rotation of the constricted arcdischarge. The constricted arc rotates about the longitudinal axis of the arc-tube here in this example about a radius of about 5 millimeters. The constricted arc itself is approximately l-2 mm. in diameter during operation. The constricted arc-discharge rotates at the frequency of the power supply 26, which is for example cycles. The radial distance from the arc-tube longitudinal axis about which the arc rotates can be readily varied by varying the magnetic flux resultant which interacts with the are, or by varying the frequency of rotation of this magnetic flux. The magnetic fluxshould also not be so great that the resulting force drives the constricted discharge against the arc-tube wall.

It is also possible to utilize only two conductive turns as the electromagnetic means when the arc-tube is operated with a DC power supply. For example, in FIG. 3 two conductive coils 30a, 30b are spaced proximate the arc-tube with their central axes perpendicular to each other as well as both being transverse to the longitudinal axis of the arc-tube. The power supply 34 can be a 90 phase shifted AC power source which is current flow in each coil.

When the arc-tube described above is operated with an AC power supply 22, for example a standard 220 VAC, 60 cycle line, this means the arc-discharge current is reversing every half cycle. In order to get the proper rotational force, the amplitude and directivity of the magnetic flux from the conductive coils 24a, 24b, 240, must be synchronous with the are current amplitude and direction. The conductive coils are again uniformly spacedabout the arc-tube, and oriented so that their respective central axis are each transverse to the longitudinal axis of the arc-tube and intersect the longitudinal axis of the arc-tube at a point which is halfway between the electrodes. The conductive coils are electrically connected to power supply 26. which in turn comprises a power selsyn generator system driven by a suitable motor as shown in FIG. 8. The primary coil 40 of the system is rotated by a conventional motor, and the coil is energized by power supply 42, the waveform of which is identical to that of power supply 22. The coil 40 may also be energized directly from power supply 22. The individual conductive coils 24a, 24b, 240 are connected respectively to the secondaries 44a, 44b, 440 of this system. This can best be understood by reference to FIG. 8, wherein the rotatable primary 40 is electrically connected to a conventional AC power supply 42. The secondary coils 44a, 44b, 440 are symmetrically disposed about the rotatable primary and are in turn connected to coils disposed symmetrically about the arc-tube. It can be appreciated that the instantaneous waveform induced in a particular secondary will depend upon the voltage waveform applied to the primary coil and also upon the spacial orientation of the primary coil with respect to the particular secondary coil. When the AC voltage waveform fed to the primary coil is the same as the AC waveform applied to the discharge device, there will be a synchronization between the discharge current direction nd and the resultant magnetic flux obtained from the coils. In this way the synchronization between arc-current characteristic and generated magnetic flux from the conducting coils is maintained. The primary coil is conveniently rotated at for example 20 cycles. In operation the constricted arc-discharge rotates at the speed of rotation of the primary coil 40 of this system, and the amplitude of the magnetic force varies with time. This is in contrast to the situation described above with the DC are, wherein the amplitude of the magnetic force was generally time independent.

The luminous efficiencies of the devices described heretofore are very high, being well over lumens per watt. The controlling of the constricted arc-discharge achieved by rotating it, prevents the early arc-tube destruction which normally follows stationary arc bowing. The rotation of the discharge insures a rather uniform temperature distribution along the arc-tube walls thereby preventing condensation of discharge sustaining materials, particularly the metallic halides.

In another embodiment of the invention as seen in FIG. 9a, 9b, the electromagnetic-field producing means comprise two coils 54a, 54b which are symmetrically disposed about the arctube 10 with the central longitudinal axis of the arc-tube being approximately coincident with the longitudinal axis of each coil. The coils are placed in planes perpendicular to each other and can be used to support the arc tube. This embodiment achieves the same result during operation with the same power supply 56 as the embodiment shown in FIGS. 3, 4 and 7. FIG. 9a is an end view of FIG. 9b which clearly shows this embodiment.

While the invention has been described by specific examples, it should be understood that the electromagnetic means which can be employed to provide the rotatably directed magnetic flux which effects the rotation of the constricted arcdischarge can be readily varied and improved upon by persons skilled in the art. It is also apparent that in a practical device the electromagnetic means could be incorporated into a lighting fixture such as shown in FIG. 5 rather than being an actual part of the commercial discharge device. In this embodiment the luminaire 46 comprises a housing 48, and a refractor 50 which is demountably attached thereto. The housing 48 mechanically supports conductive coils 52a, 52b, symmetrically about the discharge device 54 in the same manner as explained with respect to the embodiment shown in FIGS. 3 and 4. The electrical connection and operation is also the same as explained with respect to the embodiment shown in FIG. 3. The electromagnetic means could also be conveniently incorporated within an outer envelope structure about the arc-tube, which outer envelope is hermetically sealed and evacuated. Numerous other practical adaptations will be readily available to persons skilled in the art.

The rotation of the arc-discharge is observed to actually stir the gases outside the discharge about the arc-tube. This coupling of the rotating arc to the other arc-tube filling gas keeps the operating temperature of the interior wall of the arctube at manageable levels.

While the present invention has been described by reference to specific examples, the invention is not to be limited thereto or thereby. It is apparent that other metallic halides can be used in the discharge sustaining filling and charges in the electromagnetic field producing system will be apparent to those skilled in the art.

We claim:

1. A combination constricted arc-discharge device compris mg:

a. a high temperature resistant, hermetically sealed, light transmissive arc-tube;

b. lead-in conductors sealed through opposite ends of said arc-tube, and externally adapted to an operative power p y c. operatively disposed electrodes supported within said arc-tube and electrically connected to said lead-in conductors;

d. a discharge-sustaining filling contained within said aretube, and said device intended to be operated at such power input that there is maintained between said electrodes a constricted arc-discharge which is sufficiently unstable during normal operation that said arc-discharge migrates to a location proximate the wall of said arc-tube to impair the performance of said device;

e. electromagnetic flux-producing means proximate said arc-tube for producing a resultant magnetic flux which is generally transverse to and which rotates about the longitudinal axis of said arc-tube, said resultant magnetic flux intersects said arc-discharge, with the amplitude and directivity of said arc-discharge and said resultant magnetic flux synchronized to provide a predetermined resultant motor action rotational force upon said aredischarge, whereby said arc-discharge rotates about the arc-tube longitudinal axis to improve the performance of said device.

2. The device as specified in claim 1, wherein said discharge sustaining filling comprises mercury, inert fill gas, and selected metallic halide.

3. The combination as specified in claim 1, wherein the resultant motor action is determined to preferably cause said constricted arc-discharge to rotate about said arctube longitudinal axis approximately midway between said axis and said arc-tube wall.

4. The device as specified in claim 1, wherein said electromagnetic means comprise a plurality of conductive turns disposed symmetrically about the central longitudinal axis of said arc-tube, the central axis of said turns being generally transverse to said arc-tube central longitudinal axis, said conductive turns being energized by power supply means to provide a resultant magnetic flux which is rotatably directed transverse to said constricted arc-discharge.

5. The combination as specified in claim 1, wherein when said combination comprises a direct current operative power supply for said arc-discharge device, said electromagnetic means comprise a plurality of conductive turns symmetrically spaced about the central longitudinal axis of said arc-tube, with the central axis of each of said turns intersecting the longitudinal axis of said arc-tube proximate the midpoint between the electrodes, and said conductive turns are powered by a power supply to thereby provide a rotatably directed resultant magnetic flux.

6. The combination as specified in claim I, wherein said electromagnetic means comprise two conductive coils and a power supply which provides a phase shifted AC voltage waveform.

7. The combination as specified in claim 1, wherein when said combination comprises an alternating current operative power supply for said arc-discharge device, said electromagnetic means comprises a plurality of conductive coils and a power supply which provides a rotatably directed resultant magnetic flux varying in amplitude and directivity in synchronization with the arc-discharge current.

8. The combination as specified in claim 1, wherein said electromagnetic flux producing means is mechanically mounted in a luminaire fixture which is adapted to receive said discharge device.

9. The combination as specified in claim 1, wherein said electromagnetic means comprise three conductive coils and a power supply which provides a three phase AC voltage waveform.

10. A combination constricted are-discharge device comprising:

a. a high-temperature-resistant hermetically sealed, lighttransmissive, elongated arc-tube having electrodes operatively disposed therein, and electrically connecting to lead-in conductors sealed through opposite ends of said arc-tube;

b. a predetermined discharge-sustaining filling contained within said arc-tube, said lead-in conductors connected to an operative power supply to maintain between said electrodes a constricted arc-discharge of predetermined electrical characteristics and power consumption, and said constricted arc-discharge unless controlled being sufficiently unstable that it will migrate to a location proximate the wall of said arc-tube and impair the performance of said device; and

c. electromagnetic flux-producing means proximate said arc-tube for producing a predetermined density of magnetic flux along the longitudinal axis of said arc-tube, said magnetic flux is generally transverse to and rotates about the longitudinal axis of said arc-tube, and said magnetic flux and said constricted arc-discharge bearing such relationship to one another that the resultant motor action on said arc-discharge causes said are discharge to rotate about the longitudinal axis of said arc-tube in a path which is spaced from said arc-tube wall. 

1. A combination constricted arc-discharge device comprising: a. a high temperature resistant, hermetically sealed, light transmissive arc-tube; b. lead-in conductors sealed through opposite ends of said arctube, and externally adapted to an operative power supply; c. operatively disposed electrodes sUpported within said arctube and electrically connected to said lead-in conductors; d. a discharge-sustaining filling contained within said arctube, and said device intended to be operated at such power input that there is maintained between said electrodes a constricted arc-discharge which is sufficiently unstable during normal operation that said arc-discharge migrates to a location proximate the wall of said arc-tube to impair the performance of said device; e. electromagnetic flux-producing means proximate said arc-tube for producing a resultant magnetic flux which is generally transverse to and which rotates about the longitudinal axis of said arc-tube, said resultant magnetic flux intersects said arc-discharge, with the amplitude and directivity of said arcdischarge and said resultant magnetic flux synchronized to provide a predetermined resultant motor action rotational force upon said arc-discharge, whereby said arc-discharge rotates about the arc-tube longitudinal axis to improve the performance of said device.
 2. The device as specified in claim 1, wherein said discharge sustaining filling comprises mercury, inert fill gas, and selected metallic halide.
 3. The combination as specified in claim 1, wherein the resultant motor action is determined to preferably cause said constricted arc-discharge to rotate about said arc-tube longitudinal axis approximately midway between said axis and said arc-tube wall.
 4. The device as specified in claim 1, wherein said electromagnetic means comprise a plurality of conductive turns disposed symmetrically about the central longitudinal axis of said arc-tube, the central axis of said turns being generally transverse to said arc-tube central longitudinal axis, said conductive turns being energized by power supply means to provide a resultant magnetic flux which is rotatably directed transverse to said constricted arc-discharge.
 5. The combination as specified in claim 1, wherein when said combination comprises a direct current operative power supply for said arc-discharge device, said electromagnetic means comprise a plurality of conductive turns symmetrically spaced about the central longitudinal axis of said arc-tube, with the central axis of each of said turns intersecting the longitudinal axis of said arc-tube proximate the midpoint between the electrodes, and said conductive turns are powered by a power supply to thereby provide a rotatably directed resultant magnetic flux.
 6. The combination as specified in claim 1, wherein said electromagnetic means comprise two conductive coils and a power supply which provides a 90* phase shifted AC voltage waveform.
 7. The combination as specified in claim 1, wherein when said combination comprises an alternating current operative power supply for said arc-discharge device, said electromagnetic means comprises a plurality of conductive coils and a power supply which provides a rotatably directed resultant magnetic flux varying in amplitude and directivity in synchronization with the arc-discharge current.
 8. The combination as specified in claim 1, wherein said electromagnetic flux producing means is mechanically mounted in a luminaire fixture which is adapted to receive said discharge device.
 9. The combination as specified in claim 1, wherein said electromagnetic means comprise three conductive coils and a power supply which provides a three phase AC voltage waveform.
 10. A combination constricted arc-discharge device comprising: a. a high-temperature-resistant hermetically sealed, light-transmissive, elongated arc-tube having electrodes operatively disposed therein, and electrically connecting to lead-in conductors sealed through opposite ends of said arc-tube; b. a predetermined discharge-sustaining filling contained within said arc-tube, said lead-in conductors connected to an operative power supply to maintain between said electrodes a constricted arc-discharge of predetermined electrical characteristics and power consumPtion, and said constricted arc-discharge unless controlled being sufficiently unstable that it will migrate to a location proximate the wall of said arc-tube and impair the performance of said device; and c. electromagnetic flux-producing means proximate said arc-tube for producing a predetermined density of magnetic flux along the longitudinal axis of said arc-tube, said magnetic flux is generally transverse to and rotates about the longitudinal axis of said arc-tube, and said magnetic flux and said constricted arc-discharge bearing such relationship to one another that the resultant motor action on said arc-discharge causes said arc discharge to rotate about the longitudinal axis of said arc-tube in a path which is spaced from said arc-tube wall. 